This invention relates to improved sheet feeding apparatus for separating sheets of material individually from a stack of such sheets placed on a sheet receptacle and translating them to a processing device, and more particularly to a sheet feeding apparatus for feeding paper sheets by air suction of each sheet.
In the systems provided with a paper feeding apparatus for separating a single sheet of paper individually from a stack of such sheets, for example, in paper feeding apparatus for feeding original documents to be transmitted, such as employed in a facsimile system, accurate separation and feeding of paper is required, and in practice, the originals to be transmitted vary in their quality, stiffness and other characteristics. Thus the conventional paper separating and feeding apparatus employing corner claws is of no use in this field.
Therefore, in the field of facsimile systems, attention has been directed to a paper feeding apparatus using air suction, which is operative by drawing the top sheet of the stack by air suction, and such apparatus has already been put into practical use. One example is shown in FIG. 1 wherein reference number 1 indicates an axial fan. The axial fan 1 has a suction port which is located at a position corresponding to opening 2a formed in suction box 2 disposed beneath the axial fan 1. In the suction box 2, feed roller 3 is mounted, which is connected to a drive source (not shown) for rotation in the direction of the arrow. Also in the suction box 2, vacuum plate 4, forming the bottom of the suction box 2, is pivotally supported by support shaft 5. In the vacuum plate 4, opening 4a is formed at a position corresponding to the feed roller 3 so as to allow the roller 3 to fit therein. Below the vacuum plate 4, sheets 6 are stacked on sheet receptacle 7, their leading ends being aligned vertically.
While the apparatus is not operated, the forward end of the vacuum plate 4 is held in contact with the top sheet as indicated by chain line 4A.
Upon a command to feed paper, the feed roller 3 begins to rotate in the direction of the arrow and at the same time the axial fan 1 is actuated to evacuate air from the suction box 2. Thus top sheet 6a is drawn into contact with the vacuum plate 4 at about the opening position 4aA. The opening 4a is closed by the sucked sheet 6a, and the vacuum plate 4 is lifted to a solid line position as it is drawn by the sucking action. At this time, the feed roller 3, rotating in the direction of the arrow, extends through the opening 4a and is brought into contact with the sucked sheet 6a, with the result that the roller translates the sheet 6a by friction in the direction of the arrow a.
The manner in which the sheets are brought into contact with the vacuum plate 4 by suction may also be as follows. Since the sheets 6 have their leading ends pressed down by the forward end portion of the plate 4, the top sheet 6a may not easily separate from sheet 6b, stacked immediately beneath it, when the two sheets are clinging together, and at this time, the sheet 6b may also be moved upwardly as shown in FIG. 2. However, particularly in a facsimile system, such an accident as a plurality of sheets being lifted and fed together must be obviated in feeding the originals to be transmitted. Also, feeding of a plurality of paper sheet causes a paper jam.